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Injury and Yield Responses of Soybean to Chronic Doses of Ozone and Sulfur Dioxide in the Field. Allen S. Heagle, Plant Pathologist, Southern Region, USDA Agricultural Research Service, North Carolina State University, Box 5397, Raleigh, North Carolina 27607; Denis E. Body(2), and Grady E. Neely(3). (2)(3)Mechanical Engineer and Biologist, respectively, Environmental Protection Agency, National Ecological Research Laboratory, Corvallis, Oregon 97330. Phytopathology 64:132-136. Accepted for publication 6 July 1973. DOI: 10.1094/Phyto-64-132.

Beginning 14 days after emergence, ‘Dare’ soybean plants were covered by chambers and exposed for 6 h per day to ozone (O3), sulfur dioxide (SO2) and a mixture of these gases. The chamber treatments were carbon filtered air (CF), 5 pphm O3 (low O3), 10 pphm O3 (high O3), 10 pphm SO2 (SO2), and 10 pphm O3 + 10 pphm SO2 (mix). Plants were also grown outside in ambient air (AA). Injury, growth, and yield of plants were evaluated 43, 92, and 133 days after exposures began. Sulfur dioxide alone or in the mix did not significantly affect these responses. Low O3 caused injury and defoliation but did not significantly reduce growth or yield. High O3 and the mix caused injury and defoliation and reduced growth and yield. Injury was usually somewhat greater, and yield somewhat less, in the mix than in the high O3, but these differences were not statistically significant. The results show that soybean can sustain some ozone injury without loss of yield. The results suggest that, unless acute episodes occur which cause extensive foliar injury, soybean yield will not be reduced in areas with seasonal daily 6-h averages of less than 5 pphm O3 or 10 pphm SO2.

Additional keywords: air pollution, field exposures, field chambers, Glycine max.